访问范围外的变量而不传递它们？

Question

Is there a way to access variables outside their class?

class MyClass1
{
public:
    int x;
};

class MyClass2
{
public:
    int get_x()
    {
        //somehow access MyClass1's variable x without 
        //passing it as an argument and return it.
    }
}

int main()
{
    MyClass1 obj1;
    obj1.x = 5;
    MyClass2 obj2;
    std::cout << obj2.get_x();
    return 0;
}

One of the main things making me reluctant to split my programs into many small organized classes rather than a few messy huge ones is the hassle of passing every single variable that one class might need from another. Being able to access variables without having to pass them (and having to update both declarations and definitions should something change) would be very convenient and would let me code more modually.

Any other solutions to my issue would also be appreciated, as I suspect there may be something dangerous about trying to access variable this way.

Answer 1

The only way you can get access to the x of MyClass1 is if you have an instance of that class, because x is not static .

class MyClass2
{
public:
    MyClass2(MyClass1* c1) : myC1(c1) {}
    int get_x()
    {
        return myC1->x;
    }
private:
    MyClass1* myC1;
}

Then you can use this like

int main()
{
    MyClass1 obj1;
    obj.x = 5;
    MyClass2 obj2{&obj1};
    std::cout << obj2.get_x();
    return 0;
}